The overall objective of this proposal entitled, Mechanisms Regulating Hemangioendothelioma: A Plastic Surgeon's Challenge, is to determine how nox-4 regulates the growth of endothelial cells that develop into tumors and to determine whether the biological products that result from nox-4 derived oxidants can be used as biomarkers. Nox-4 is the catalytic subunit of the enzyme NADPH oxidase that converts molecular oxygen to superoxide as the first step in endogenous reactive oxygen species production that serves many functions in the cell. We have used an established murine model where injection of endothelial (EOMA) cells results in formation of a hemangioendothelioma, and have shown that hemangioendothelioma formation is nox-4 dependent. This proposal combines the expertise of a multidisciplinary group of investigators including a surgeon-scientist, molecular biologist, and radiologist. Collectively, we will utilize the unique resources and infrastructure of the Hemangioma and Vascular Malformation Clinic at Nationwide Children's Hospital and the Laser Capture Microscopy Core housed in the Davis Heart Lung Research Institute at Ohio State University Medical Center and these entities are linked by the Clinical Translational Science Award funded Center for Clinical and Translational Science to create a novel translational approach to investigating hemangiomas and hemangioendotheliomas in children. These are the most common soft tissue tumors in children, they can be extremely disfiguring and the most effective treatment options all have life-threatening side effect profiles. A critical barrier to improving the clinical outcomes for affected children is the lack of low risk treatment options. The goal of this proposal is to address that critical barrier by identifying potential new treatment targets and establishing biomarkers that can be used to design and execute scientifically rigorous clinical trials. The goals and objectives for this grant will be achieved through the following 3 specific aims: 1) Determine the mechanisms through which nox-4 derived oxidants induce EOMA to form hemangioendothelioma. 2) Characterize the significance of let 7f microRNA down regulation in unleashing high nox-4 expression in EOMA. 3) Determine whether nox-4 derived oxidant inducible urinary 8-OHdG and serum MCP-1 levels can be used as biomarkers to monitor growth and involution of HE in children. Successful execution of this proposal will advance the knowledge base for hemangioendothelioma by discovering new therapeutic targets responsible for mediating the effects of nox-4 derived oxidant production on hemangioendothelioma formation, providing first evidence of microRNA that silence nox-4, and performing the first prospective longitudinal study in this patient population to identify biomarkers. This would result in a paradigm shift in both the clinical and basic science investigative approaches by emphasizing the importance of endogenous oxidant production in hemangioendothelioma formation and by introducing the concept of microRNA directed therapeutics to treat hemangioendotheliomas.